When I was around 5 my parents warned me several times that if I fell from a height then I would break my neck.
I figured that since my body was heavier than my head, my body would fall faster than my head and the two parts would seperate at the neck while falling.
A childhood belief about physics

others believed things like this
- i used to belive that if i fell on my head my head would come off while i was doing a cartwheelAnon
- I used to believe lepers came from Ireland. Like leprechauns, only with less body parts.Anon
- I used to think that bodily tissues were kleenex sheets that grew in certain parts of your body.Anon
- I used to believe that a funeral organist was the person who collected the body parts of the deadAnon
- I used to think that "extra body" shampoo meant you could use the runoff suds to clean your body.— Christy
- I used to believe that the lungs where tubes in the neck.— Some Guy